IGCSE - 0417

System Analysis and Design

What is Systems Analysis?

Systems Analysis is, as the name states, the analysis of systems!

The systems that we are talking about are the systems within organisations and businesses - systems of communication, financial systems, manufacturing systems, etc. - basically the systems that make the organisation or business work.

A person who analyses systems is known as a Systems Analyst.

Often systems analysts are employed by organisations of businesses to help them improve their systems and so become more efficient, and for businesses, more profitable.

Stages of Designing a New SystemResearch – Collecting information about

how the present system works.Analysis - Examining out how the present

system works and identifying problems with it

Design - Coming up with a new system that will fix the present systems problems

Production - Creating the new system from the design.

Testing - Checking if the newly created system works as expected

Documentation - Creating documents that describe how to use the new systems, and how it works

Implementation - Replacing the present system with the new system

Evaluation - Checking that the new system meets all expectations

Researching the Present System

Before the systems analyst can make any recommendations about a new system, they first have to understand how the present system works.

This can be done by – Gathering Information – through Observation, Interviews or Questionnaires

Collecting Documents

Analyzing the Present System

Having collected as much information about the present system as possible, the systems analyst now looks though it all to understand how the system works, and to try and identify problems that need to be fixed.

This process is called analysis.

Identifying the Inputs, Outputs and ProcessesEvery system has inputs and outputs and thesystems analyst needs to identify the data input to the present system, and the data output.This is because any new system that is designed will have to deal with similar inputs and outputs as the present system.

For example, the payroll system in a business might have the following inputs and outputs...

Any new system that is created will need to take in the same input data (the number of hours worked by employees), and will have to produce the same three outputs.

For similar reasons, the systems analyst also has to understand how the present system works (the processes – who does what and when)...

Identifying ProblemsNo system is perfect and it is the job of the

systems analyst to try and identify where the problems in a system are.

If these problems can be fixed, the system will work more smoothly, be more efficient and, in the case of a business, be more profitable.

In the above payroll example, the following problems might be identified...The payroll often takes over three days to process, resulting in many employees being paid late

Timesheets sometimes get lost before being processed. This means that sometimes pay has to be estimated

The reports sent to management do not show enough information.

New System Requirements Specification

Now the problems with present system are understood, the system analyst can begin to plan how the new system will fix those problems.

The systems analyst specifies a list of requirements for the new system (‘requirements’ simply means targets or aims).

This list is usually called the Requirements Specification.

For the payroll example the requirements might be...Payroll processing should be completed within 24 hours

The recording of hours worked should use a system that means the data cannot be lost

Management reports should contain detailed information about pay for each department, overtime payments and average hours worked by each employee

Management reports should be electronic so that managers can analyse the data more easily

Any new system that is designed must meet these requirements.

What Hardware and Software Will Be Required?

The systems analysts will now need to decide what hardware and software will be required for the new system...

HardwareHow many computers?

What type of network?How many servers?Any special input devices? (e.g. barcode

readers)Any special output devices?Software

Is ready-made, off-the-shelf software available?

Is custom-written software required?

Designing the System Inputs

To get data into a system is a two-part process:Data must first be ‘captured’ (collected in a

way that then makes it easy to input)Data must be input into the computer

The systems analyst will select a data capture method and data input method that best suit the requirements of the new system.

Data Capture Methods

Manual through Paper Forms which is filled inAutomatic – Through Barcode reader, Card

Reader, CameraDesigning an onscreen form for filling in details.

This should –Have all of the necessary fieldsHave obvious places for user input (boxes, use of

colour, etc.)Use appropriate controls (see below) for each

fieldHave text box controls that are the right size for

the dataHave easy-to-understand instructions (if needed)Make good use of the screen area available

Data Validation Techniques When data is input to a computer, it is a good idea for the

computer to check that the data is sensible Different validation checks can be used on different fields,

depending on the type of data being entered...

Presence Check Is data actually present in a field, or has it been missed

out? Range Check Is the data value within a set range?

(E.g. an exam mark should be between 0% and 100%, a month should be between 1 and 12)

Length Check Is an item of text too short or too long? Type Check Is the data the correct type?

(E.g. the letter ‘A’ should not be allowed in a numeric field)

Format Check Is the data in the correct format?

(E.g. a date of b

Data Verification Techniques Data validation only checks whether the data entered is

sensible - it does not mean that the data is the right data.

To check that data is the correct value, we use a system called data verification.

There are two methods of data verification... Proof Reading After the data has been entered a person compares the

original data with the data in the computer (either on the screen or using a print-out).

If mistakes are spotted they can be corrected by the person.

Proof-reading is quick and simple, but doesn’t catch every mistake.

Double-Entry The data is entered into the computer twice

(preferably by two different people).

The computer compares the two sets of data to see if they match. If not it generates an error and a person will need to correct the mistake.

Designing the System Processes

Designing Data and File StructuresWhen designing a database, the system designer

needs to consider:The type of data being stored (numbers, text, dates, etc.)

The size of the data (how long is a typical name, etc.)

The field names to useHow many records will need to be storedThe designer also need to consider which

backing storage device and media will be suitable to store the data:How often will the data need to be accessed

How quickly the data needs to be accessedHow large will the data files be

Designing the System OutputsThere are usually two types of output from

a system that need to be designed:On-screen reports (information displayed on the monitor)

Printed reports (hard-copy to be mailed, filed, etc.)

On-screen reports should...Show all of the necessary fields

Have fields that are the right size for the dataHave easy-to-understand instructions (if

needed)Make good use of the screen area availableMake good use of colours and fonts to make

the data clear

Designing Printed ReportsDesigning a printed report is just like

designing an on-screen report (see above), except that the report needs to fit a piece of printer paper, rather than the screen. The report might also include page numbers, a header / footer, etc

Testing Data A test plan is usually written whilst the system is being

developed. The test plan will contain details of every single thing that needs to be tested.

For example:Does the system open and close properly?

Can data be entered? Can data be saved? Can reports be printed? When you do something wrong, does an error message

appear? Is invalid data rejected? E.g. if you are not allowed to

enter an amount above £1,000 on the system then a value of 1,001 should not be accepted (i.e. does the validation work?)

Test plans are very detailed, and contain many tests. Each test is specified very precisely. A typical test would contain:Details of what is being tested

The test data to use What is expected to happen when the test is performed

Selecting Test Data

Normal Data Values This is data that would normally be entered

into the system in a specified given range. Eg- Any data between the range of 0-100

The system should accept it, process it, and we can then check the results that are output to make sure they are correct.

Extreme Data Values Extreme value are still normal data.

However, the values are chosen to be at the absolute limits of the normal range. Eg- 100 or 500

Abnormal Data Values This is data that should not normally be

accepted by the system - the values are invalid.

The system should reject any abnormal values. Data outside the specified range should be rejected. Eg- if the range is between 100-500, then any no less than 100 or greater than 500 is the abnormal value

Abnormal values are used in testing to make sure that invalid data does not break the system.

When is the System Tested?Testing is normally done in two stages...

The first phase of testing is done by the designers and engineers who created the system, usually before the system is delivered to the customer.

The test data that is used in this first phase is similar to data that would be used by the actual customer.

The second phase of testing is done after the system has been delivered and installed with the customer.

The data used in the second phase is usually 'live' data - data that is actually part of the customer's business / organisation.

What Happens if the System Fails Some Tests?

The whole point of testing is to try and find areas that don't work as they should, or areas that can be improved.

If any failures are found, the systems analyst goes back and does some further research, analysis and design to fix these areas.

Documenting the New System

There are two types of documentation that should be produced when creating a new system:User documentation

Technical documentationUser documentation usually includes:

List of minimum hardware and software required to use the system

How to install the systemHow to start / stop the systemHow to use the features of the systemScreenshots showing the system in typical useExample inputs and outputsExplanations of any error messages that might be

shownA troubleshooting guide

Technical documentation usually includes:Details of the hardware and software required for the system

Details of data structures (data types, field names, etc.)

Details of expected inputsDetails of validation checksDetails of how data is processedDiagrams showing how data moves

through the systemFlowcharts describing how the system

works

Implementing the New System

Direct ChangeoverThe old system is stopped completely,

and the new system is started. All of the data that used to be input into the old system, now goes into the new one.

This is has its advantages...Takes the minimal time and effort

The new system is up and running immediately

But there are also disadvantages...If the new system fails, there is no back-up system, so data can be lost

Parallel RunningThe new system is started, but the old system

is kept running in parallel (side-by-side) for a while. All of the data that is input into the old system, is also input into the new one.

Eventually, the old system will be stopped, but only when the new system has been proven to work.

This is has its advantages...If anything goes wrong with the new system, the old system will act as a back-up.

The outputs from the old and new systems can be compared to check that the new system is running correctly

But there are also disadvantages...Entering data into two systems, and running two systems together, takes a lot of extra time and effort

Phased ImplementationThe new system is introduced in phases

(stages, or steps), gradually replacing parts of the old system until eventually, the new system has taken over.

This is has its advantages...Allows users to gradually get used to the new system

Staff training can be done in stagesBut there are also disadvantages...

If a part of the new system fails, there is no back-up system, so data can be lost

Pilot RunningThe new system is first of all piloted (trialed) in

one part of the business / organisation (e.g. in just one office, or in just one department).

Once the pilot system is running successfully, the new system is introduced to the all of the business / organisation.

This is has its advantages...All features of the new system can be fully trialed

If something goes wrong with the new system, only a small part of the organisation is affected

The staff who were part of the pilot scheme can help train other staff.

But there are also disadvantages...For the office / department doing the pilot, there is no back-up system if things go wrong

What Does an Evaluation Look For?

When the systems analyst evaluates the new system, the following questions will be asked:

Is the system... ...efficient? Does it operate quickly, smoothly and with minimal waste?

Is the system saving time, and resources? ...easy to use? Are all of the system's users able to use the system easily

and effectively?

Can new staff understand and use the system with minimal training?

...appropriate? Is the system suitable for the particular business /

organisation?

Does the system actually meet the needs of the business / organisation?

How is a System Evaluated?

The systems analyst will use a number of techniques to evaluate the system...

Check against the Requirements Specification

If you remember, earlier on in the Systems Analysis, the old system was analysed, and a checklist of targets was drawn up for the new system.

This list was called the Requirements Specification.

The systems analyst will use this document to check the new system. Going through the requirements one-by-one the analyst will check if they have been met.

Check the Users' Responses

It is essential to get feedback from the users of the system... Do they like it?

Does it make their work easier? What, if anything, could be improved? The systems analyst can get this feedback in the same way they

collected information about the original system...Questionnaires

Interviews Observation